Foundations that have settled due to weak or unstable soil conditions must not only be raised to their original level, but the underlying earth must be reinforced or stabilized to prevent further settling. A number of methods and devices have been proposed for remedying these problems.
Langenbach, Jr., et al., U.S. Pat. No. 4,563,110, teaches a shoring apparatus and method comprising a piling member that is lowered through a hole in the concrete floor. The piling member rotates about a vertical axis to bear down upon the earth and exert an upward force on the floor. Haekkinen, U.S. Pat. No. 4,567,708, discloses a method for raising a floor wherein a hole is made in the floor and then pressurized foam is sprayed between the floor and the underlying earth to create pressure to thereby raise the floor. A disadvantage of these and other similar methods is that they first require a hole to be drilled in the concrete slab. In many applications, this is not possible or would be extremely expensive. In addition, the device for raising and supporting the floor bears down on or rests upon the sunken and unstable earth, thus creating the potential for additional settling of the floor or slab.
David, U.S. Pat. No. 4,338,047, teaches a system for pier underpinning of a settling foundation. A pier of concrete and pipes is constructed directly beneath the foundation footing, a mechanical jack is then arranged immediately underneath the foundation footing and on top of the pier, and after the jack has raised the foundation footing, additional concrete is poured beneath the foundation footing to encapsulate the mechanical jack. Freeman, U.S. Pat. No. 3,269,126, discloses a method for stabilizing and raising foundation structures that involves excavating a hole beneath the foundation wall, placing a pipe having a conical end flange and an intermediate barrier flange in the hole, then filling the hole with concrete. After the concrete has set, a plastic, hard-setting composition is pumped through the pipe to force the concrete and the abutting foundation upwards. A disadvantage of these and other similar methods is the cost of leaving expensive jacks and other equipment in the ground. A further disadvantage is the cost of excavating a deep cavity beneath foundation. Another drawback of the latter method is that the hardsetting composition will seep into the ground as it dries, thus allowing the foundation to resettle.
Another method requires a large hole to be dug underneath the sunken foundation. Post holes are then dug in the bottom of the hole to a depth of approximately five feet. Concrete is then poured in the post holes and the large hole to create a piling upon which is rested a jack. The jack is formed from an opened-top container having a thick layer of rocks or gravel in the bottom onto which concrete is poured to create a block. After the concrete has dried, a thin mixture of cement and water is pumped into the container through a side opening near its bottom to force the concrete block out of the top of the container to contact and lift the sunken foundation. This method has numerous disadvantages. First, the post holes often are not deep enough to reach stable soil. As a result, the pumping of the cement and water mixture into the container to lift the foundation forces the pilings to sink into the ground instead of lifting the foundation. Another disadvantage is that the concrete poured over the rocks or gravel to form the block can seal up the opening in the container and prevent the cement and water mixture from being pumped therein.
This invention is directed to a method and apparatus for raising and supporting a foundation that overcomes the foregoing and other problems of prior methods and devices.